MATRIX VISION - mvBlueCOUGAR-X/-XD Technical Documentation
Triggering of an indefinite sequence with precise starting time

Scenario

Especially in the medical area, there are applications where a triggered acquisition is started, for example, with a foot switch. Following challenges have to be solved in combination with these applications:

  • The user wants the acquired image immediately (precise starting time).
  • It is not known, when the user stops the acquisition (indefinite sequence).

Using AcquisitionStart as the trigger source, it could take between 10 and 40 ms until the camera acquires the first frame. That's not really an immediately acquisition start. It is recommended to use FrameStart as the trigger source instead. However, according to the time the trigger event occurs, there will be a timeout during the first frame in nearly all cases.

You can avoid this using a timer which generates a "high" every 100 us and which is connected to the trigger input Line4 using a logical AND gate. I.e. if the timer is "high" and there is a trigger signal at Line4 then the logical conjunction is true. The AND gate result is then connected as TriggerSource of the FrameStart trigger using a logical OR gate. I.e. as soon as the logical AND conjunction is true, the trigger source is true and the image acquisition will start.

The following figure illustrates the settings:

Figure 1: Schematic illustration of the settings

With this setting, there is still an acceptable time delay of approx. 100 to 130 us possible.

Creating the use case using wxPropView

First of all, we have to set the timer in "Setting -> Base -> Camera -> GenICam -> Counter And Timer Control" with following settings:

Property name wxPropView Setting
Timer Selector Timer1
Timer Trigger Source Timer1End
Timer Duration 100.000

Afterwards, we have to set the logical gates in "Setting -> Base -> Camera -> GenICam -> mv Logic Gate Control" with following settings:

Property name wxPropView Setting
mv Logic Gate AND Selector mvLogicGateAND1
mv Logic Gate AND Source 1 Line4
mv Logic Gate AND Source 2 Time1Active
mv Logic Gate OR Selector mvLogicGateOR1
mv Logic Gate OR Source 1 mvLogicGateAND1Output

Finally, we have to set the trigger in "Setting -> Base -> Camera -> GenICam -> Acquisition Control" with following settings:

Property name wxPropView Setting
Trigger Selector FrameStart
Trigger Mode On
Trigger Source mvLogicGateAND1Output
Trigger Activation RisingEdge
Exposure Mode Timed
Figure 2: Sample settings